In general, blow-by gas generated in an internal combustion engine is high-pressure and high-temperature combustion gas and is leaked through a gap between a piston ring and a groove. Such blow-by gas contains unburned hydrocarbon, evaporating substance of engine oil, carbon particles and moisture which cause an environmental pollution when the blow-by gas is discharged to the atmosphere.
Therefore, in order to meet the vehicle exhaust gas regulation, a blow-by gas recirculation system (closed crankcase ventilation) is applied to the engine and an oil separator is applied to the blow-by gas recirculation system to remove oil components from the blow-by gas.
The oil separator includes a drain cup for collecting and discharging separated oil and a gas passage cup for discharging gas obtained by separating the oil from the blow-by gas, together with a gas flow guide.
Therefore, once the blow-by gas containing the oil and the gas in an engine crankcase enters the oil separator, the oil and the gas are separated from each other in the oil separator by the blow-by gas flow using an internal structure. Then, the oil is drained to an oil pan through the drain cup and the gas is conveyed to an intake duct through the gas passage cup.
As described above, since the oil separator separates the oil contained in the blow-by gas and collects the separated oil in the oil pan, it is possible to prevent evaporative components from adversely affecting on the components constituting the engine.
However, since the oil separator employs a cap, a diaphragm, a spring, cubs for the gas passage and the gas flow guide, a blow-by gas sucking guide, a case for an oil separation and a drain cup as the essential components, the size of the oil separator increases by a relatively large number of components, an excessive size of the oil separator causes a disadvantage in a weight and is disadvantage in terms of a package for mounting the engine.
A complicated internal structure in which the components constituting the oil separator are correlated with each other causes rise of manufacturing cost of the oil separator. Due to an excessive rise of cost, the above oil separator is disadvantage in terms of manufacturing cost.